The present invention relates to a cutting device for a face-to-face weaving machine, comprising a cutting knife and an upper and a lower cutting rail with an intermediate distance which may be adjusted by means of one or several screw means.
By intermediate distance, in this patent application, is meant: the distance between the upper and the lower cutting rail (=jaw).
In face-to-face weaving machines two fabrics are woven simultaneously one above the other which most of the time are interconnected by pile warp yarns moving from the lower cloth to the upper cloth and inversely, forming the pattern.
The two fabrics are kept apart from one another at a distance determined by the opening between the lower and the upper rail, provided a sufficient tension is applied to the warp yarns. The face-to-face fabrics not yet separated are kept apart from one another at the distance between the upper and the lower cutting rail (=jaw), before being presented to the cutting movement.
Adjusting this intermediate distance (jaw) is a delicate operation, as much as:                to adjust a certain value of the jaw;        to keep the height of the jaw at the same value at the left and right of the weaving machine;        to keep the cutting device in a central position with respect to the jaw.        
In the Belgian patent BE 8.701.167 a device is described which simplifies the adjusting of the jaw and with which applying the “trial and error method” is no longer needed where after each readjustment the jaw has to be checked by weaving a piece of fabric. To that effect, the cutting device is provided with one or several electronic motion detecting devices giving a signal which is related to the position of the upper and the lower rail respectively with respect to the cutting knife. When readjusting the adjusting spindles, which, according to this patent, are driven by an electric motor, the distances between the upper and the lower cutting rail on the one hand and between one of the cutting rails and a fixed point of reference on the weaving machine (top or bottom side of the cutting knife) on the other hand, may be read and verified, or the processor unit may be operated to control the drive and, in doing so, to reach the position desired. On the one hand, the adjusting spindles used to that effect are adjusting spindles adjusting the height of the jaw (moving the upper cutting rail with respect to the lower cutting rail or inversely) and on the other hand, adjusting spindles moving the adjustment of the jaw with respect to the cutting rail (moving upper and lower cutting rails as a whole with respect to the cutting knife). The method emanating from this operation has the disadvantage that, when adjusting a new height of the jaw by moving the upper cutting rail with respect to the lower cutting rail (or inversely) the cutting knife will be moved from the centre of the jaw and has to be readjusted by means of other adjusting spindles. This method is laborious and may be the cause of errors.
The invention according to BE 8.701.167 also allows the upper and the lower cutting rail each to be equipped with one or several adjusting spindles allowing a movement between the cutting knife and the upper and the lower cutting rail respectively. In this embodiment, first the upper rail, for instance, is adjusted with respect to the cutting knife and thereafter the lower cutting rail is adjusted with respect to the cutting knife. This method also remains laborious, because both the upper and the lower cutting rail have to be adjusted separately. When adjusting the height of the jaw, the position of the cutting knife will not remain in the centre of the jaw and this may likewise be the cause of errors or inaccuracies.
Driving the adjusting spindles by means of electric motors and using the processor unit in order to reach the position desired, will simplify the adjustment and will reduce the risk of errors and inaccuracies, but it is an expensive solution for operations which have to be carried out only occasionally.